1. Field of the Invention
The present invention relates to an imprint apparatus for transferring a surface structure of a stamper onto a surface of material to be patterned.
2. Description of the Related Art
Recently, integrating (fining) techniques for a semiconductor integrated circuit have been advanced. In order to realize such a fine fabrication, more preciseness has been pursued in pattern fabrication of a semiconductor integrated circuit by using a photolithographer, for example. On the other hand, needs in such a fine fabrication have almost reached a limit to shorten wavelength of an exposure light source, so that ultra-fining techniques have been facing a limit of fine patterning. Consequently, for the sake of achieving an even higher preciseness of pattern fabrication, there are utilized an electron beam lithography apparatus which is a variation of a charged particle beam apparatus, taking the place of a photolithography apparatus.
However, in an electron beam lithography patterning, the more patterns to be patterned by an electron beam there are, the longer exposure (patterning) time is needed, which is different from a case of a batch exposure using a light source such as i-ray or excimer laser. Consequently, as integration of a semiconductor integrated circuit is advanced, longer time for pattern fabrication is required, which results in significant decrease in throughput.
In order to enhance pattern fabrication speed by using an electron beam lithography apparatus, a batch graphic radiation method has been developed, in which masks in a variety of shapes are combined and exposed to an electron beam at a time. However, an electron beam lithography apparatus utilizing this batch graphic radiation method becomes bigger in scale and requires a further system for controlling mask positions at a high accuracy, which brings a problem of higher cost in the entire apparatus itself.
As another pattern fabrication technique, an imprint method has been known, in which a predetermined stamper is pressed so as to transfer a surface structure thereof. In this imprint method, a stamper provided with projected and recessed patterns reversely corresponding to projected and recessed patterns to be pattered is pressed onto a surface of material to be patterned, whereby a fine structure with a width between each projected and recessed patterns of 25 nm or less is fabricated on the material to be patterned. Such an imprint method can fabricate fine patterns in a lower cost, for example, in a process of manufacturing mass storage media or semiconductor integrated circuits.
In this imprint method, it is necessary to previously align the stamper with the material to be patterned at a high accuracy before pressing the stamper onto the material to be patterned.
Conventionally, as a method for aligning a stamper with material to be patterned, such a method has been known, in which there is provided alignment patterns on each surface of the stamper and the material to be patterned. Then, the alignment patterns are monitored in an optical way so as to align the stamper with the material to be patterned (as disclosed in Patent Documents 1 and 2, for example). In this method, since the alignment is carried out in an optical way, a high accuracy of the alignment can be achieved. However, this method has a disadvantage in that alignment patterns have to be provided on both the stamper and the material to be patterned, which causes the manufacturing process more complicated. In this method, there is also another disadvantage in that this method cannot be applicable to such a case, for example, of a disk substrate for magnetic recording medium with which substantially no alignment patters can be provided.
To counter this problem, there has been known another method for aligning a stamper with a disk substrate for magnetic recording medium, in which an adjusting pin is inserted in each center hole having an approximately same diameter, which is provided on a disk substrate and a stamper respectively (Patent Documents 3, 4, 5, for example). In this method, an alignment pin is inserted into the center holes of the stamper and the disk substrate which are stacked and aligned to each other, whereby they are aligned at a position where each hole thereof are stacked and aligned. In this way, this method provides a horizontal alignment between a disk substrate and a stapmer in a simple process without providing special alignment patterns.    Patent Document 1: JP 2000-323461A    Patent Document 2: JP 2005-116978A    Patent Document 3: WO 03/104898 A    Patent Document 4: U.S. Pat. No. 6,757,116 B    Patent Document 5: JP 2005-100584A
However, in such an alignment method using an alignment pin (see Patent Documents 3, 4, 5, for example), since an alignment is performed while a stamper and a disk substrate are stacked, air bubbles are likely to be involved between the stamper and the disk substrate, that is, on a surface to be transferred. To counter this problem, it may be considered that a stamper and a disk substrate are aligned in a vacuum atmosphere so as to eliminate such bubbles between the stamper and the disk substrate. However, even under a vacuum atmosphere, it is impossible to completely eliminate the bubbles between the stamper and the disk substrate as far as they are placed in a stacked condition. Remaining bubbles may cause a problem of hindering an accurate pattern fabrication.
Therefore, it has been desired to provide an imprint apparatus and method for preventing bubbles from remaining between a stamper and material to be patterned, so as to realize a high accurate pattern fabrication.